角膜内皮细胞培养的研究进展

角膜内皮功能失代偿引起的失明可通过角膜移植来治疗.人们通过体外培养角膜内皮细胞并使其增殖,进行角膜内皮细胞移植和角膜组织工程学研究.目前常用的分离角膜内皮细胞的方法是从供体上撕除后弹力层和角膜内皮层,利用酶消化作用使角膜内皮细胞分离.常用的培养基为基础培养基加各种生长因子.这些生长因子在一定程度上促进细胞增殖,但培养的角膜内皮细胞长期传代后仍难以维持正常的细胞形态和功能.基因转染技术建立了永生化角膜内皮细胞系,有关细胞周期、信号通路和离子通道的研究成果也促进了角膜内皮细胞体外培养的研究进展.本文综述了角膜内皮细胞体外培养各个环节的最近进展.     

Cryopreservation and lentiviral-mediated genetic modification of human primary cultured corneal endothelial cells

PURPOSE: To determine the viability and potential usefulness of cryopreserved human primary cultured corneal endothelial cells by characterizing their morphology, gene expression, and ability for genetic modification by the lentiviral vector equine infectious anemia virus (EIAV). METHODS: Primary cultured endothelial cells were dissociated from human corneas and grown in organ culture medium. Corneal endothelial cell origin was confirmed by morphology and immunostaining with polyclonal anti-collagen VIII antibodies. Cells of different passages were cryopreserved in medium containing dimethyl sulfoxide and were assessed after thawing for morphology, proliferative capacity, gene expression, and ability to form cell-cell junctions. EIAV encoding enhanced green fluorescent protein (eGFP) was used to transduce cryopreserved human corneal endothelial cells. Transduced cells were then sorted by fluorescence-activated cell sorting (FACS) and imaged with fluorescence microscopy. RESULTS: Cryopreserved, primary, cultured human corneal endothelial cells are viable and retain their ability to proliferate, produce collagen VIII, and express ZO-1, a tight-junction protein. EIAV-based gene transfer of eGFP is highly efficient and nontoxic to cryopreserved human primary cultured corneal endothelial cells. These genetically modified cells can be selected to nearly pure populations with FACS sorting. CONCLUSIONS: Human primary cultured corneal endothelial cells retain their phenotypic properties after cryopreservation. The ability to store, genetically modify, and sort these cells through FACS to pure populations has the potential to greatly expand their future therapeutic application to treat corneal endothelial disorders.     

小鼠角膜基质细胞的KSFM培养基培养法

目的研究使用KSFM培养基能否获取具有增殖能力且保持生物学特性不变的小鼠角膜基质细胞（CSCs）。方法实验研究。将中央区角膜置于EDTA液（20mmol／L）内孵育45min后,用手术显微镊小心剥离角膜上皮层以及内皮层,并将获取的角膜基质置于含300U／mlⅠ型胶原酶的溶液中消化4h。离心后采用DMEM基础培养基、DMEM完全培养基（含10％FBS）以及KSFM培养基重悬细胞常规培养,并以含1U／m1分散酶的EDTA液消化传代细胞。同时,观察细胞并绘制细胞生长曲线;采用逆转录聚合酶链式反应（RT．PCR）检测细胞角膜蛋白多糖（keratocan）mRNA和乙醛脱氢酶（ALDH）mRNA表达情况;采用细胞免疫荧光染色以及蛋白质印迹方法检测细胞keratocan蛋白的表达情况。采用独立样本≠检验对数据进行统计学分析。结果通过胶原酶消化的方法可以从每只小鼠的角膜基质获取约l×l04个单个细胞。RT-PCR结果显示,原代细胞表达CSCs标记物keratocan和ALDH;免疫荧光染色和蛋白质印迹结果显示：原代细胞表达keratocan蛋白。培养于DMEM基础培养基内的原代CSCs无法增殖。培养于DMEM完全培养基内的CSCs可增殖,但第3代细胞不表达keratocan mRNA和ALDH mRNA以及keratocan蛋白。培养于KSFM培养基内的CSCs也可增殖,第3代细胞仍表达keratocan mRNA和ALDH mRNA以及keratocan蛋白,且与原代细胞相比,表达强度差异无统计学意义。结论KSFM培养基不仅能维持小鼠CSCs的生物学特性不变,还能有效促进细胞增殖。     

Isolation and long-term cultivation of human corneal endothelial cells

Human corneal endothelial cells (HCEC) were isolated by means of enzymatic treatment of excised corneas. The corneas were incubated for 1.5 hr together with a high concentration of collagenase (0.5%), followed by a long-term incubation (up to 16 hr) using a low concentration of the enzyme (0.04%). Endothelial cells were enriched against contaminating fibroblasts by using a selective L-valine-free medium which inhibited fibroblast growth during the first passages. Subcultures of HCEC were passaged for more than 20 generations without showing signs of senescence. Laminin and chondroitin sulfate functioned as a substrate for HCEC, promoting proliferation and allowing the cells to grow in monolayer formation. The inclusion of fibroblast growth factor (FGF) as well as chondroitin sulfate in the medium led to an additional increase in the rate of proliferation.     

Growth of human corneal endothelial cells in culture

We investigated the effects of various culture conditions on the growth of normal human corneal endothelial cells in culture. Falcon Primaria tissue culture plastic was found to provide a more suitable surface for endothelial cell growth than the conventional Corning tissue culture plastic. Also, media containing 10% fetal bovine serum and 5% calf serum (complete media) facilitated the growth of human cells better than those containing Nu-serum. Supplementation with epidermal or fibroblast growth factor (10 and 100 ng/ml) to the complete media had no effect on human endothelial cell growth. Chondroitin sulfate at low concentrations (100 micrograms/ml to 1 mg/ml) also showed little effect. At high concentrations (13.5 and 25 mg/ml), however, chondroitin sulfate significantly promoted human corneal endothelial cell growth during a 1- to 2-week incubation period. From the 37 cultures initiated, outgrowth from explants appeared within 3 to 7 days. Cells were polygonal in shape and, at confluency, formed a continuous monolayer. We attained a success rate of 87% (7/8) growing primary cultures from donors under 20 years of age and a 59% (17/29) success rate from older donors.     

In vitro culture of human fetal corneal endothelial cells

Purpose  

To explore and optimize a proper culture system for human fetal corneal endothelial cells (hFCECs), including the methods of primary culture, passage and cryopreservation.     

角膜基质细胞条件培养液促进角膜内皮细胞增生的研究

目的 探讨人胚胎角膜基质细胞(human embryonic C01Tleal stromal cells,hECSC)条件培养液对人胚胎角膜内皮细胞(human embryonic corneal endothelial cells,hECEC)体外增生的影响.方法 将生长融合达80%的原代hECEC用0.125 g·L-1胰蛋白酶/0.53 mmol·L-1EDTA传代5～10 min,第1代分3组接种于96孔板,第2天分别加入DMEM/F12(含体积分数10%FBS)、DMEM/F12(含体积分数15%FBS)和hECSC条件培养液;MTT法检测细胞增生情况;免疫荧光法对hECEC进行初步鉴定;BCA蛋白定量试剂盒检测hECSC条件培养液中蛋白含量;SPSS 11.5软件包对数据进行统计学分析.结果 MTT法检测DMEM/F12含10%FBS、DMEM/F12含15%FBS和hECSC条件培养液培养的A值分别为0.111 67±0.004 10、0.110 13±0.003 17、0.122 53±0.004 10,多组方差分析显示,条件培养液组与其他2组相比差异均有统计学意义(P均<0.05);免疫荧光结果显示hECSC呈NSE和ZO-1阳性染色;BCA蛋白定量结果显示hECSC条件培养液中总蛋白浓度为871.385 mg·L-1.结论 hECSC条件培养液对hECEC的体外生长增生有促进作用,其应用和其中活性成分分析有待进一步的研究.     

Life span of human corneal endothelial cells in long-term cultures

Human corneal endothelial cells (HCEC) were isolated from excised corneas of adult donors in the age range of 28-70 years, and successfully grown for 10-12 passages. Moreover, one cell line, that had been established from a 45-year-old donor, was further passaged at defined split ratios in order to determine the proliferative life span of the HCEC isolated from donors of this age group.     

角膜内皮细胞改良培养技术的初步探讨

目的 评价角膜后弹力层撕除联合酶消化法分离角膜内皮细胞的效率,分析细胞体外生长的生物学特性.方法 将兔角膜带有内皮细胞的后弹力层完整撕下,用胰蛋白酶-EDTA联合酶消化,纯化的角膜内皮细胞进行体外培养.观察细胞形态,用神经元烯醇化酶抗体进行细胞表型鉴定.苏木精-伊红染色以及茜素红-台盼蓝联合染色分析细胞活性,流式细胞仪检测细胞体外生长过程中Anne xiv-PE的表达情况,透射电镜和扫描电镜进行细胞超微结构形态的观察.结果 带角膜内皮细胞的后弹力层撕除联合酶消化法可快速获得大量纯化的角膜内皮细胞,快速贴壁生长并增生,体外培养3～4d即融合成单层细胞,且表达神经元烯醇化酶抗体阳性,苏木精-伊红染色及活性染色提示细胞功能良好,Annexiv-PE抗体表达水平微弱.结论 角膜后弹力层撕除联合酶消化法可提高角膜内皮细胞的获取和培养效率,为工程化角膜内皮移植膜的构建提供稳定的种子细胞来源.     

Human corneal endothelial cells: isolation, characterization and long-term cultivation

Long-term cultures of human corneal endothelial cells have been established. In culture, these cells form a dense monolayer (about 500,000 cells cm-2), similar to that found in vivo, and synthesize an extracellular matrix containing laminin, entactin, and fibronectin. Factor VIII and angiotensin-converting enzyme were not found in either the cultured or native corneal endothelium. Cells were obtained by scraping corneal buttons that had been preincubated in the culture medium supplemented with endothelial cell mitogen. The human corneal endothelium was grown under conditions virtually the same as those used for cultivation of human vascular endothelial cells, namely, on fibronectin- or gelatin-coated tissue culture plastic in Medium 199 supplemented with 20% human serum and 400 micrograms ml-1 endothelial cell growth supplement. Human corneal endothelial cells from the culture obtained can be used for transplantation onto human corneas, for studying repair of damaged corneal endothelium in situ, as well as for in vitro studies of cell growth regulation.     

Expression and activity of cell cycle-regulatory proteins in normal and transformed corneal endothelial cells.

Corneal endothelial cells have a limited capacity for proliferation. Upon transformation with the SV40 large T antigen, however, these cells undergo division and grow rapidly. In order to gain insight into the control mechanisms that determine this proliferative switch, we investigated the expression level and activity of various known cell cycle-regulatory proteins in these cells. Primary human and rabbit corneal endothelial cells were transduced in vitro with a replication-defective adenovirus containing SV40 large T antigen, and subsequently the expression and activity of cell cycle-regulatory proteins was analyzed. Cells transduced with large T antigen exhibited strongly increased activity of cyclin-dependent kinases. This increase correlated with the elevated expression of various cyclin-dependent kinase subunits, such as cyclin A, and to a lesser extent, cyclin D, cdk2, and cdk4. Furthermore, the expression of two cyclin-dependent kinase inhibitors, p21(WAF1) and p27(KIP1), which was high in primary human cells (but not in primary rabbit cells), was strongly reduced in large T-antigen transduced cells. Thus, the remarkably low proliferative activity of normal human corneal endothelial cells appears to be regulated at two levels: the expression of certain cell cycle-regulatory proteins that are essential for cell cycle progression is extremely low (cyclin A) or somewhat low (cdk2 and cdk4); but the amount of p21 and p27, inhibitors of cell cycle progression, is very high. As a consequence, the enzymatic activity of cyclin-dependent kinase is below detectable levels. However, the growth-inhibitory status of these components is clearly reversible: upon transduction with large T antigen, the expression of cyclin A, cyclin D, cdk2, and cdk4 is induced, whereas the expression of p21 and p27 is inhibited, and the cells proliferate. Thus, our study provides insight into the molecular basis of the attenuated proliferation of corneal endothelial cells and suggests potential targets that could be manipulated for the purpose of therapeutic interventions aimed at renewed cell growth.     

人角膜上皮与内皮细胞培养的改进

介绍一种简便、实用、材料来源相对充足的人角膜上皮、内皮细胞培养方法－－酶消化培养法。７－９天能形成良好的单层角膜上皮细胞；２０天左右形成的密集的单层人角膜内皮细胞。这一方法适于我国角膜病实验应用。     

兔角膜内皮细胞球形培养的活性和细胞表型

背景 组织工程角膜内皮层的构建和细胞注射疗法需要足够数量的角膜内皮细胞（CECs）,因此如何在体外培养大量高活性的角膜内皮种子细胞是当前亟需解决的问题. 目的 建立兔CECs高活性三维（3D）球形培养方法,探索培养细胞的生物学特性. 方法 酶消化法分离和培养兔CECs并进行传代,经低黏附振动培养法产生兔CECs球,倒置相差显微镜下观察培养细胞的形态;采用扫描电子显微镜观察CECs球的表面超微结构;用吖啶橙染色法鉴定CECs球中细胞的活性;采用CCK-8试剂盒检测细胞的吸光度（A450）值,判断细胞的增生情况.将CECs球接种到6孔细胞培养板贴壁培养1周,球形培养的细胞为球形培养组,常规培养的细胞为常规培养组.采用免疫荧光法检测闭锁小带蛋白1（ZO-1）和Na＋/K＋-ATP酶在细胞中的表达.结果 经球形培养的CECs呈聚集生长,培养1周细胞形态为六角形或多边形,融合成单层,呈铺路石状排列;扫描电子显微镜下可见兔CECs球体周围有细胞爬出,未长散的细胞球中细胞与细胞之间结合紧密,球体表面凹凸不平.吖啶橙染色表明,细胞球中90％细胞呈绿色荧光;球形培养组细胞平均A450值为1.524±0.013,常规培养组细胞平均A450值为1.265±0.021,球形培养组细胞增生值明显增加,2个组间差异有统计学意义（t=-3.436,P=0.010）.免疫荧光检测表明,培养的细胞中ZO-1和Na＋/K＋-ATP酶阳性细胞膜对FITC呈绿色荧光,细胞核DAPI染色呈蓝色荧光.结论 CECs的3D球形培养方法培养的细胞可保持细胞的高活性、高增生能力和细胞表型,为构建组织工程角膜内皮及细胞疗法提供了更好的角膜内皮种子细朐.     

无血清器官培养法保存大鼠角膜内皮细胞的活性

目的:研究两种新型培养基-内皮细胞培养基(endothelial cell medium,ECM)和无动物成分培养基(animal compoundfree medium,ACF)在无血清器官培养法保存角膜内皮细胞活性方面的应用效果。方法:将大鼠角膜密闭保存于ECM和ACF培养基中4wk,再经葡聚糖T500脱水2d。以含低浓度牛血清的MEM基础培养基作为对照。计数保存前后角膜内皮细胞密度,检测保存结束大鼠角膜内皮层中胞质紧密粘连蛋白1(zonula occludens-1,ZO-1)的表达水平,评估内皮细胞层的屏障功能。结果:保存结束后,MEM+20mL/L FBS对照组大鼠的角膜内皮细胞密度值最低,ECM+20mL/L FBS组则高达2250±202个/mm2,ECM和ACF组结果与ECM+20mL/LFBS组接近,细胞死亡率也较低,组间差异有统计学意义(F=28.965,P=0.000)。冰冻切片显示ZO-1在保存后大鼠角膜内皮层成功表达。RT-PCR检测表明ZO-1mRNA在各组的表达趋势与内皮细胞密度结果一致(F=592.751,P=0.000)。结论:无血清ECM和ACF培养基可以很好地保持器官培养法保存角膜内皮细胞的活性和紧密连接的屏障功能。     

家兔角膜内皮细胞的快速培养

目的:短期内体外扩增获得角膜内皮细胞。方法:采用揭膜法与消化法相结合获取原代角膜内皮细胞。并采用本实验室自行研制的角膜内皮细胞培养体系,在24孔培养板中分别以1×106,5×105,1×105,5×104,1×104,5×103细胞/孔浓度传代培养细胞,观察细胞的生长情况。结果:以1×105～5×105个细胞/孔浓度的细胞悬液并添加消化后的Descemet膜原代培养细胞,4d后细胞形成与在体细胞相似的密集单层,可以快速获取纯化的角膜内皮细胞。传代培养时,虽然不同接种浓度在4d的细胞增殖倍数差异不显著,但以1×105～5×105个细胞/孔的浓度传代,3d就可生长成密集单层并可继续传代,现已传至第10代,但传至第4代,细胞形态开始发生改变;而以5×105个细胞/孔以上的浓度传代细胞时,1d的细胞贴壁率下降;以5×104个细胞/孔以下浓度传代,需7d方可长满皿底,并且细胞开始老化,体积变大,不能继续传代培养。或者细胞不能铺满皿底就衰老死亡。结论:本实验的培养体系可在短期内获得实验用角膜内皮细胞。角膜内皮细胞体外培养的增殖能力与其培养浓度和增殖的空间有关,1×105～5×105个细胞/孔的浓度是角膜内皮细胞快速增殖的适宜培养浓度。     

高糖对兔角膜内皮细胞的形态学影响

目的：研究高糖环境下兔角膜内皮细胞形态学的变化。方法：用细胞培养的方法模拟体内高糖环境,原代培养兔角膜内皮细胞,用倒置相差显微镜和扫描电镜对高糖组及地照组进行形态学观察及分析比较。结果：高糖组角膜内皮细胞出现肿胀、六边形细胞比例减少、细胞间隙增大、细胞表面出现裂纹、微绒毛消失、细胞核皱缩等一系列的形态学改变,且这种改变程序与葡萄糖浓度基本呈正相关。结论：高糖对角膜内皮细胞存在影响,提示糖尿病病人角膜内皮细胞的修复和代偿能力下降,故当糖尿病病人进行眼部手术或存在眼部病变、损伤时,注意保护角膜内皮细胞非常重要。     

Transplantation of corneal endothelial cells

Though conventional corneal transplantation has achieved great success, it still has several drawbacks including limited availability of donor corneas, recurrent allograft rejection, and subsequent graft failure in certain cases. Reconstructing clinically usable corneas by applying the technology of regenerative medicine can offer a solution to these problems, as well as making corneal transplantation a non-emergency surgery and enabling the usage of banked corneal cells. In the present study, we focused on corneal endothelium that is critical for corneal transparency and investigated the reconstruction of cornea utilizing cultured human corneal endothelial cells (HCECs). We succeeded in steadily culturing HCECs by using culture dishes pre-coated with extracellular matrix produced by calf corneal endothelial cells and culture media that contained basic fibroblast growth factor and fetal bovine serum. We performed the following analysis utilizing these cultured HCECs. The older the donor was, the more frequently large senescent cells appeared in the passaged HCECs. The telomeres of HCECs were measured as terminal restriction fragments (TRF) by Southern blotting. HCECs, in vivo from donors in their seventies had a long TRFs of over 12 kilobases. Passaging shortened the TRFs but there was no difference in TRFs among donors of various ages. These results indicated that shortening of telomere length is not related to senescence of HCECs. We investigated the role of advanced glycation end products (AGEs) in the senescence of in vivo HCECs. The results indicated that AGE-protein in the aqueous humor is endocytosed into HCECs via AGE receptors expressed on the surface of HCECs and damages HCECs by producing reactive oxygen species and inducing apoptosis, suggesting that AGEs, at least partly, cause the senescence of HECEs. HCECs were cultured using adult human serum instead of bovine serum to get rid of bovine material that can be infected with prions. Primary and passage culture of HCECs was possible using adult human serum. We reconstructed the cornea using cultured HCECs and human corneal stroma. The corneal stroma, on which the cell suspension of HCECs was poured, was mildly centrifuged to enhance the HCECs attachment to the stroma. The cell density of HCECs on the reconstructed cornea reached 2,500 cells/mm2. The pump function of the reconstructed cornea was measured with an Ussing chamber. The potential difference in the reconstructed cornea and normal cornea was 0.30 mV and 0.40 mV, respectively; indicating that the pump function of the reconstructed cornea is 75% of that of the normal cornea. The reconstructed cornea was transplanted to a rabbit eye and stayed transparent for 6 months after the operation. Fluorescein labeled cultured HCECs remained on the graft 1 month after the transplantation, indicating that transplanted HCECs contributed to the transparency of the graft. The possibility of using artificial stroma or porcine corneal stroma as a carrier of cultured HCECs was investigated. The artificial stroma made of alkaline-treated collagen could not be sutured but showed good transparency, biocompatibility, and cell-attachability. Porcine corneal stroma, expressing little xeno-sugar antigen alpha-gal epitope, induced no super acute rejection but mild cellular rejection when transplanted in the cornea of animals possessing natural antibody to alpha-gal epitope. The cornea reconstructed with porcine corneal stroma and HCECs had an average cell density of 1721/mm2 and had approximately 60% of the pump function of a normal cornea. As new technologies in corneal transplantation, the application of self immature cells and the direct delivery of cultured HCECs into the anterior chamber were investigated. Part of rat mononuclear cells that were obtained from the bone marrow and injected into the rat anterior chamber transformed into corneal endothelium-like cells, suggesting that self immature cells can transform into corneal endothelial cells. Cultured rabbit corneal endothelial cells that endocytosed iron were injected into the anterior chamber of rabbits whose corneal endothelium was cryo-injured, and were pulled to Descemet's membrane by putting a magnet on the eyelid. In these rabbits, corneal edema decreased more quickly than in the control group and no intraocular pressure rise was observed during 8 weeks after the operation, suggesting that the direct delivery of cultured HCECs into the anterior chamber can be an alternative method of choice. The following obstacles should be addressed to make the transplantation of cultured corneal endothelial cells clinically applicable. 1. To reconstruct a cornea that is the same as or superior to the normal cornea, more innovation is necessary in the method of culturing and seeding HCECs. We should consider utilizing HCECs obtained from fetuses after clearing ethical issues. Moreover, we need to develop a method to enhance the cell density and the cell functions. 2. Porcine corneal stroma is promising as a carrier of HCECs instead of human corneal stroma, which is in very limited supply. The usefulness of porcine corneal stroma acellularized to prevent retrovirus infection should be evaluated. 3. To make the self immature cells applicable to corneal transplantation, we should elucidate the corneal endothelial cell specific markers and the factors that are necessary to induce self immature cells to become corneal endothelial cells. 4. The direct delivery of cultured HCECs into the anterior chamber can be an alternative method of choice when its long-term safety is confirmed.